1. Field of the Invention
The present invention relates to an apparatus for controlling an object's height above or distance from a surface and more particularly to an apparatus that can be used to give an indication of the distance from the ground of an aircraft and cause the aircraft to be controlled within some predetermined distance.
2. Description of the Prior Art
Various means have been developed for controlling the distance between an object or vehicle moving over a surface and the surface. For example, some powered model aircraft have control cables held at one end by an operator while the other end is attached to the flying aircraft thereby limiting the altitude of the aircraft to the length of the control cable. Similar tether devices have been used to limit the height of balloons and helicopters. Being able to control distance would also be very useful in such fields as crop dusting or flight training.
Other altitude control devices include for example, flaps located at the trailing edge of an aircraft's wings, or airbrakes consisting of pivotable flaps attached to the fuselage of the aircraft which are retracted in a position flush with the body of the aircraft during normal flight and are extended outwardly toward a more perpendicular position relative to the fuselage when braking is desired; the extended disposition increases parasite drag on the aircraft which in turn causes the aircraft's flight path to become more downwardly inclined relative to the horizontal.
Yet another form of aircraft control device, directed more toward velocity control, is an attached parachute which is normally folded within the body of an aircraft in normal flight and is extended only upon landing; the parachute's main function upon landing is to shorten the runway necessary to complete landing.
A more recent device used to increase drag of a flying object (which incidentally is not an altitude control device but a velocity control device) is exemplified by U.S. Pat. No. 3,374,973 to D. P. Lokerson. In that patent, a drag device consisting of a plurality of banners are stowed in a vehicle such as a rocket until the remaining portion of the rocket returns to the Earth. At this time, the banners are extended and provide a drag which the patentee believes is "caused primarily by energy transfer resulting from banner flutter and attendant air turbulence." (Column 2, lines 59 through 61). While the devices mentioned are useful in controlling altitude and/or velocity, none has been shown to effectively control the altitude or distance from the ground of an aircraft (or other object) and yet not interfere with the aircraft's maneuverability or performance when the distance from the ground is within a predetermined value or set of values.
Of course any apparatus that is devised would have to be economically feasible to warrant patent protection and to have commercial value.